Metallic honeycomb panels or sandwich structures have been increasingly used on advanced designs for vehicles such as aircraft and ships. Reasons for using metallic sandwich structures include saving weight as compared to steel structures, reducing radar cross section increasing corrosion resistance, and reducing life cycle costs.
Although such sandwich structures can offer certain superior bending stiffness properties over other design configurations, one issue that may tend to limit the usage of sandwich structures is the difficulty of attaching the structure to adjacent structures or attachment fittings with adequate load transfer at the attachment region without undue increase in weight and cost. While in certain situations it can be relatively easy to attach sandwich structures when the applied loads are low, it is quite a challenge to do so for highly loaded structure.
Various honeycomb attachment procedures have been developed. For example, one method of joining structural members such as metallic structural members utilizes a core ramp down region. In such a process, the honeycomb core residing between the facing sheets must be eliminated either through the fabrication of the core or must be machined down after core manufacturing. Such processes are expensive, they also still require some type of attachment fitting between the honeycomb panel and some other supporting structure, and may be prone to certain heightened failure modes if the ramp down is either too steep or too shallow.
Alternatives to core ramp-down include the use of mechanical inserts, bushings, or other types of mechanical attachment fittings that must be integrated within the panel. However, the use of such attachment fittings can also present certain shortcomings. For example, to install certain fittings within a panel, a section of the panel must be cut out and a machined fitting is inserted into the panel or must be welded to the face sheets of the panel. This increases the overall cost of the sandwich structure while also increasing the time to manufacture as well.
There is, therefore, a need for a more cost effective and less labor intensive method of assembling honeycomb core structures. Such a desired cost effective and less labor intensive assembled structures should also offer a more robust and efficient method of providing a seal to the edges of a honeycomb panel while also increasing manufacturing facility throughput while also driving down overall system manufacturing costs.